MongoDb C# Driver 2.0 add item to nested array

Question

I have a Profiles document collection with array of the following documents :

public class Profile2MailList
{


    [BsonElement(elementName: "listId")]
    [BsonRequired]
    public int MailListId;

    [BsonElement(elementName: "status")]
    [BsonRequired]
    public int Status;

    [BsonElement(elementName: "subscriptionDate")]
    [BsonRequired]
    public DateTime SubscriptionDate;
} 

in each Profile. I need to add to the Profile2MailList array a new Profile2MailList document in each Profile based on Profile2MailList which already contains in a certain Profile. So i need to

• Take needed profiles from Profiles collection
• Update Profile2Maillist array in each Profile

• Run update command How can i perform that action via C# 2.0 MongoDb Driver. I have MongoDb v 3.0.2. I try to make it by the following way :

     List<Profile> listProfiles = new List<Profile>();
              foreach (Profile item in profiles)
              {
                  item.MailLists.ToList().Add(new Profile2MailList(maillistId, item.MailLists.FirstOrDefault().Status));
                  var t = item;
                  listProfiles.Add(t);
              }
      dbCollection.UpdateManyAsync(listProfiles)
  

Answer 1

The method "UpdateManyAsync" only works if you want to perform one type of update, which doesn't seem to be your case. What you want to do is perform a Bulk-Update instead. Building on your example, you would want to do something like:

        var bulk = new List<WriteModel<Profile>>();
        foreach (Profile item in profiles)
        {
            var newProfile = new Profile2MailList(maillistId, item.MailLists.FirstOrDefault().Status);
            var filter = Builders<Profile>.Filter.Eq(g => g.Id, item.Id);
            var update = Builders<Profile>.Update.AddToSet(item.MailLists, newProfile);
            var updatemodel = new UpdateOneModel<Profile>(filter, update);

            bulk.Add(updatemodel);  
        }
        await profileCollection.BulkWriteAsync(bulk);

The AddToSet operator adds a value to an array unless the value is already present.